Benzothiazine-1,1-dioxides

ABSTRACT

Novel carbonate esters of 3-heteroarylcarbamyl-4-hydroxy-2H-1,2benzothiazine 1,1-dioxides are disclosed. The esters have therapeutic properties in antiinflammatory, anti-thrombotic and analgesic applications.

United States Patent Rasmussen Dec. 9, 1975 [5 BENZOTHIAZINE-1,1-DIOXIDES 3,853,862 12/1974 Lombardino 260/243 [75] Inventor: Chris Royce Rasmussen, Ambler,

Pa Primary Examiner-John M. Ford [73] Assignee: McNeil Laboratories, Incorporated,

Ft. Washington, Pa.

[22] Filed: Sept. 23, 1974 Appl. N0.: 508,116

US. Cl 260/243 R; 424/246 Int. Cl. C07D 279/02 Field of Search 260/243 R [57] ABSTRACT Novel carbonate esters of 3-heteroarylcarbamyl'4- hydroxy-ZH-l,2-ben20thiazine l,l-dioxides are disclosed. The esters have therapeutic properties in antiinflammatory, anti-thrombotic and analgesic applications.

2 Claims, N0 Drawings BENIJOTHIAZIN E- l ,l-DIOXIDES DESCRIPTION OF THE INVENTION This invention relates to novel carbonate esters of 3- heteroarylcarbamyl-4-hydroxy-2H-l ,2-benzothiazine l,l-dioxides, and more particularly to the esters represented by the formula CONH-Ar (I) In this and succeeding formulas, R is lower alkyl, R is lower alkyl, aryl or aralkyl, and Ar is heteroaryl.

[n the foregoing definitions of R and R, the expression lower alkyl" refers to a straight or branched hydrocarbon chain having from 1 to about 6 carbon atoms, such as for example, methyl, ethyl, propyl, isopropyl, sec.-butyl, pentyl, isoamyl, n-hexyl, isobutyl, 2-hexyl, etc. The preferred aryl" radical is phenyl and the preferred aralkyl" radical is benzyl. The expression heteroaryP' refers to 2-thiazolyl, 3-isoxazolyl and monoand dimethyl substituted 2-thiazolyl and 3-isoxazolyl, such as 4-methyl-thiazol-2-yl, S-methyl-isoxazol-3-yl, 4,5-dimethylthiazol-2-yl, and 4,5-dimethylisoxazol-3-yl.

The preferred compounds are those in which R is methyl, and R is methyl, ethyl, phenyl or benzyl.

The novel compounds of Formula I are generally crystalline solids soluble in organic solvents such as dimethyl formamide, dimethyl sulfoxide, ethers such as dioxane, dimethyl ether of diethylene glycol, tetrahy drofuran and the like, ketones such as acetone, Z-butanone, etcl, and halohydrocarbons such as 1,2- dichloroethane, chloroform, etc. Generally, they are of low solubility in such solvents as petroleum hydrocarbons and water.

The novel carbonate esters of Formula I have numerous utilities. For example, they are useful as anti-inflammatory agents for alleviating the painful symptoms of arthritis and other inflammatory disorders. The compounds also are useful an antithrombotic agents adapted to be employed for the treatment of cardiovascular disease s. In addition, the compounds are useful as analgesic agents.

The novel carbonate esters of the present invention may be prepared by reacting a benzothiazine dioxide compound represented by the formula:

CONH-Ar with a chloroformic ester represented by the formula (l-C-O-R' (III) in the presence of a base. (It is to be understood that the reactant benzothiazine dioxides represented in Formula ll in the enolic form, in the case of certain compounds may partially exist in the tautomeric keto form. It is also to be understood that although the reactions are described in terms of a chloroformic ester, other haloforrnic esters may be substituted, if desired.) The preparation of the carbonate esters is preferably carried out in a solvent medium, either aqueous or organic, and the temperature range of from about 0 to about 50C as hereinafter more fully described. The exact amounts of the reactants are not critical but for good yields, especially under aqueous conditions, it is desirable to use molar excessess of the chloroformic ester and the base.

In one method for carrying out the reaction, the starting material of Formula ll is dissolved in an aqueous alkaline solution and the chloroforrnic ester is added thereto portionwise and with stirring while the pH is maintained in the range of from about 8 to about l2. The aqueous alkaline solution is preferably of aqueous alkali hydroxide such as sodium hydroxide, potassium hydroxide and the like, or aqueous alkali carbonate such as sodium carbonate, potassium carbonate and the like. The reaction is exothermic and it is desirable to add the chloroformic ester in a portionwise manner. The reaction may be further moderated by using a large volume of solvent and/or cooling. When the reaction is carried out in an aqueous solvent, some of the chloroformic esters tend to undergo hydrolysis; thus, it is desirable to use excess chloroformic ester. From two to ten-fold molar excess may be employed. Since the hydrolysis of the ester removes the base necessary for the primary reaction to proceed, excess base is preferably employed also. Such amounts of base are added to maintain the pH in the range of from about 8 to l2. As a result of these operations, a reaction takes place with the formation of the desired carbonate ester product which generally precipitates as a solid in the reaction mixture and an inorganic salt by-product. The product may be recovered by filtration and pu rified by conventional procedures such as washing, recrystallization, etc.

An alternative method for carrying out the reaction is particularly useful when the starting material of Formula II is of low solubility in the aqueous alkaline media. ln this method, the compound of Formula ll is dissolved in an organic solvent and a base added thereto as a first step whereupon there is formed a conjugate base of the starting material. Thereafter, the chloroformic ester is added portionwise with stirring to obtain the desired carbonate ester product and chloride salt by-product. Suitable solvents for carrying out the reaction include hexamethylphosphoric acid triamide, N,N- dimethylformamide, dimethyl sulfoxide, and the like; ethers such as tetrahydrofuran, dioxane, LZ-dimethoxyethane, dimethyl ether of diethylene glycol and the like; aromatic hydrocarbons such as benzene, toluene, xylene, and the like; lower alkyl ketones such as ace tone, Z-butanone, and the like; lower alkyl esters such as ethyl acetate, n-amyl acetate, and the like; and nitro gen heterocyclic solvents such as pyridine, picoline, lutidine, and the like. Suitable bases include nitrogen bases such as triethylamine, l,4-diazabicyclo-[2,2,2]-

3 octane, N,N,N ',N'-tetramethyll ,S-diaminonaphthalene, and the like; inorganic bases such as sodium hydride. lithium hydride. and the like; organometallic bases such as methyl magnesium halide, n-butyl lithium, phenyl lithium and the like. When the solvent employed is a basic organic nitrogen compound such as pyridine, picoline, etc., it may not be necessary to employ an additional base since the organic nitrogen compound can perform both functions. The carbonate ester product obtained as the result of the foregoing operations may be recovered either by vaporizing off some of the solvent or by the addition of excess cold water or dilute mineral acid depending on the solubility of the reaction solvent in water to precipitate a solid and filtering off the latter. The solid product may then be purified by conventional procedures such as washing, triturating, recrystallizing, etc.

The following examples illustrate the invention but mole), was dissolved in 800 ml of aqueous alkaline solution (prepared by adding 60 ml of sodium hydroxide to water). To this solution was added 60 ml of ethyl chloroformate in 10 ml portions with vigorous stirring after each addition while the pH was maintained between 8 and 10 by the addition of such amounts of 10% sodium hydroxide as necessary to accomplish this. As a result of these operations, the desired ethyl 2-methyl-3-(thiazol-2-yl'carbamyl)-2H-1,2- benzothiazine 1,1-dioxide-4-yl carbonate was formed in the reaction mixture as a lemon-yellow solid in a yield of 7.15 g of 87.5 percent of theoretical. The product was purified by dissolving in 1,2-dichloroethane by warming on the steam bath and recrystallizing. After repeated recrystallizations, a purified product of m.p. 203-205C was obtained.

Anal. Calcd. for C, H,,,N;,O S,: C, 46.94; H, 3.69; N, 10.26; S, 15.66. Found: C, 46.62; H 3.66; N, 10.09; S, 15.59

EXAMPLE ll In a similar operation, 6.71 g (0.02 mole) of N-(S- methylisoxazol-3-yl )-4-hydroxy-2-methyl-2H- l ,2-benzothiazine-3-carboxamide 1,1-dioxide is dissolved in aqueous alkali and 50 ml of methyl chlorofonnate added portionwise thereto with stirring while the pH is maintained between 8 and 10 to obtain a methyl 2- methyl-34S-methylisoxazol-3-yl-carbamyl)-2H-1,2- benzothiazine 1,l-dioxide-4-yl carbonate product.

EXAMPLE Ill N-(4,5-Dimethylthiazol-2-yl )-4-hydroxy-2methyl 2H- 1 ,Z-benzothiazine-3-carboxamide 1 ,l-dioxide, 7 .3 1 g (0.02 mole), is dissolved in ml of dimethyl sulfox' ide. To the resulting solution is added 2.23 ml (0.022 mole) of triethylamine to obtain the conjugate base of N-(4,5-dimethylthiazol-2-yl)-4-hydroxy-2-methyl-2H- l,2-benzothiazine-3-carboxamide l 1 -dioxide. Ben zyl chloroformate, 3.75 g (0.022 mole), is next added portionwise and with stirring to obtain the desired carbonate ester product in the reaction mixture. The reaction mixture is diluted with cold water to obtain a precipitate of benzyl 2-methyl-3-(thiazol-2-ylcarbamyl)-2 H- l,2-benzothiazine 1,1dioxide-4-yl carbonate product.

EXAMPLE IV In a further similar operation N-(4-methylthiazol-2- yl )-4-hydroxy-2-methyl-2H- l ,2-benzothiazine-3-carboxamide l, l -dioxide is dissolved in aqueous alkali and ethyl chloroformate added portionwise thereto with stirring while the pH is maintained between 8 and 10 to obtain an ethyl Z-methyl-3-(4-methylthiazol-2-yl-carbamyl )-2 PM ,2-benzothiazine l l -dioxide-4-yl carbonate product.

ln a manner similar to that described in Example lV, phenyl 3-(4,5-dimethylthiazol-Z-ylcarbamyl)-2-ethyl 2H-l ,Z-benzothiazine 1 l -dioxide-4-yl carbonate product is obtained from N-(4,5-dimethylthiazol-2-yl)-2- ethyl-4-hydroxy-2H-l ,2-benzothiazine- 3-carboxamide 1,1-dioxide and phenyl chloroformate.

EXAMPLE V1 in operations carried out employing similar molar amounts of reactants and conditions as described in Example l, the following compounds may be prepared from the appropriate N-heteroaryl-2-alkyl-4-hydroxy- 2H-l ,2benzothiazine-3-carboxamide l l-dioxide and the appropriate chloroformic ester:

Amyl 2-methyl-3-(thiazol-Zylearbamyl)-2l-ll ,Z-benzothiazine 1 l -dioxide-4-yl carbonate.

Methyl 3-(isoxazol-3-ylcarbamyl ).-2-methyl-2l-l-l ,2-

benzothiazine l 1 -dioxide-4-yl carbonate.

Benzyl 3-(isoxazol-3ylcarbamyl)-2-methyl-2l-l-l ,2-

benzothiazine 1 l -dioxide-4-yl carbonate.

Phenyl 3-(4,5-dimethylisoxazol-3-ylcarbamyl)-2-methyl-2H-1 ,2-benzothiazine 1 l -dioxide-4-yl carbonate.

The products of the present invention are useful in several chemotherapeutic applications.

One of the utilities is as an antithrombotic agent to inhibit aggregation of platelets. illustrative of the usefulness of the compounds as antithrombotic agent is the following operation: Platelet-rich plasma was prepared to contain a standardized amount (300,000/mm) of platelets. Platelet aggregation was measured by the method of Born (Nature, 194, 927 (1962)) utilizing a -fold diluted preparation of soluble (Holrnsen, Ostvold and Bay, Biochem. Pharmacol. 22, 2599 (1973)) bovine tendon collagen to induce aggregation. In a representative operation, 0.45 ml of platelet-rich plasma was treated with ethyl 2-methyl-3-(thiazol-Z-ylcarbamyl-2l-l-l ,Z-benzothiazine l l-dioxide-4-yl carbonate to give a final concentration of 10 M. Thereafter, 0.05 ml of the collagen preparation was added and the turbidity recorded. The results showed inhibition of aggregation as follows:

Concentration of The benzothiazine dioxide compound starting mateca'bonae P" F'FF rials of Formula II generally have been reported in the plasma Compound in inhibition of Source lXlO"mle5/liter[ m) Aggregation literature. A preferred method for preparing the start- Rabbi 25 80 mg materials may be represented by the following reac- Human 65 5 tion scheme:

*sccond experiment CO -Alkyl H N-Ar u 4- Al lty I -oH (IV) (v) Similar inhibition of aggregation may be obtained with Generally, 2-alkyl 4-hydroxy-3-(lower alkoxy-c arother compounds represented by Formula l. bonyl)-2H-1,2-benzothiazine-1,1-dioxide (IV) is Another property shown by the pr d cts f th presheated under reflux with an aminoisoxazole or aminoent invention is an antinociceptive effect which renders thiflZOlB p n in an inert Solvent Such as them useful as components in analgesic preparations. lehe for Several p y, With the Simulta- Antinociceptive properties of Formula I compounds fl Ous removal of the by-product alcohol to obtain the may be seen in the mouse writhing test as reported in desired 2-alkyl-3-( B-heteroarylcarbamyl)-4-hydroxy- Br. J. Pharmac. Chemother., 32, 2953l0 (1968). In a 2H-l,2-benzothiazine l,l-dioxide compound. The representative operation, mice were treated orally with preparation of 2-alkyl-4-hydroxy-3-( lower alkoxycarethyl 2-methyl-3-(thiazol-2-ylcarbarnyl)-2H-l ,Z-benm/D- 1 n 1 .lx y be zothiazine l,l-dioxide 4-yl carbonate at adosage range fo in S- Pat 5 L and 5 of 39.6 to 168.3 mg/kg. After twenty minutes the mice ternatively, the compounds of Formula ll may be prewhich had been treated (per 05) with the test compared by contacting an appropriate 2-alkyl-2H-l,2- pound and untreated controls were injected intraperibehZ0thiaZifle-4(3H)-0n L dioxide With a toneally with acetyl choline bromide (5.5 mg/kg) and h ro y isocyanate in the Presence of 3 Slight the abdominal constriction responses compared. it was la Ce ase o e Sufficient to mpl the found that ethyl 2-methyl-3-(thiaZQI-Z- Ia inOC reaction and thereafter pouring the reaction mixture bonyl)-2H-l ,2-benzothiazine 1,1-dioxide-4-yl carboninto a slightly acidic ice water to precipitate the comate was effective in reducing the abdominal constricpound of Formula II. The base may be an organic base tion responses. such as triethylamine or trimethylamine in an inert or- Additionally, the compounds have anti-inflammatory ganic solvent such as dimethyl sulfoxide or dimethylproperties rendering them useful as components in formamide. When an organic base is employed, the recompositions for combatting swelling and pain in inactants are preferably contacted under reflux for from flammatory disorders such asarthritis. A representative a few minutes to seveal hours. Alternatively, an inoroperation showing anti-inflammatory activity is the M. ganic base such as sodium hydride in a solvent such as Butyricum induced rat paw edema assay. In this test, dimethylformamide may be employed. Under these 160-190 gram rats which previously had been injected Conditions, the reactants in an anhydrous solvent are subcutaneously in one hind paw with 0.75 mg of M. added to the base. The following diagrammatic scheme Butyricum and in which by the eleventh day there had further illustrates the foregoing reaction:

l' OCN-Ar buss Ht ll R S 2 (v I) (v I) been induced edema of at least 0.25 ml were employed. The 2-alkyl-2H-1,2-benzothiazine-4(3H)-one l ,1- Test animals were closed daily for four days thereafter dioxide (VI) and heteroaryl isocyanate (Vll) comwith ethyl 2-methyl-3-(thiazol-2-ylcarbamyl)-2H-1,2 pounds employed in the foregoing synthesis are either benzothiazine l,l-dioxide-4-yl carbonate at a rate of known compounds or else can easily be prepared using mg/kg (per 05) while control animals were given saline. methods well-known to those skilled in the art, starting Comparison of the paw sizes of treated and control anifrom readily available materials. mals on the first and fifth days showed 58.6 percent Many of the chloroformic ester (Ill) starting materiedema inhibition in the paw of the treated animals. als are available commercially. Others may be prepared Similarly, edema inhibition may be observed employing readily from phosgene and appropriate alcohol by the subject compounds at dosages in the range of from methods well-known to those skilled in the art.

about 0.5 to about I00 mg/kg. What is claimed is:

7 8 l. A compound represented by the formula R is lower alkyl;

R is selected from the group consisting of lower alkyl, phenyl and benzyl; and 0 g 0 R Ar is a heteroaryl radical selected from the group consisting of Z-thiazolyl, 3isoxazolyl and mono- ONH :rzigyclli-methyl substituted Z-thiazolyl and 3-isox- ,N 2. A compound according to claim 1 which is Ethyl s Z-Methyl-3-(thiazol-2-ylcarbamyl)-2H-I,2-benzothia- O zine 1,1-dioxide-4-yl Carbonate.

wherein 

1. A COMPOUND REPRESENTED BY THE FORMULA
 2. A compound according to claim 1 which is Ethyl 2-Methyl-3-(thiazol-2-ylcarbamyl)-2H-1,2-benzothiazine 1,1-dioxide-4-yl Carbonate. 